1. Field of the Invention
The invention relates to a sensor calibration device and a sensor calibration method for calibrating, for example, a distance-measuring sensor that is mounted in a vehicle. In particular, the invention relates to a sensor calibration device and a sensor calibration method for calibrating a distance image sensor that is mounted in a vehicle.
2. Description of the Related Art
A TOF (time of flight) method that calculates the distance to a measurement object by measuring the time required for the round trip of light to the measurement object is widely known as a distance measurement method. Besides, there is developed a distance image sensor that obtains distance information by the TOF method by processing photoelectric current prior to the voltage conversion of a light reception signal, via a photogate that has a common CCD (charge coupled device) structure.
For example, an optical distance measurement device that obtains an accumulated differential signal from an Ach signal from a first accumulation element and a Bch signal from a second accumulation element by a differential computation portion is disclosed (see Japanese Patent Application Publication No. 2007-132848 (JP-A-2007-132848)). According to the optical distance measurement device described in Japanese Patent Application Publication No. 2007-132848 (JP-A-2007-132848), since the differential computation with the Ach signal and the Bch signal is performed, noise components, such as background light and the like, can be appropriately removed, and only a signal component that is needed for the calculation of the distance to the measurement object can be extracted and accumulated. Therefore, the device is able to perform highly accurate computation of distance in an environment with strong background light.
However, in the optical distance measurement device described in Japanese Patent Application Publication No. 2007-132848 (JP-A-2007-132848), since the photoelectric conversion element, such as a CCD or the like, that accumulates charges that correspond to the amount of light received changes its characteristics depending on the outside air temperature or the like, it is necessary to frequently calibrate the photoelectric conversion element in order to maintain good detection accuracy.